The National Roofing Contractors Association is pleased to provide you with this information as part of our ongoing effort to educate homeowners about roofing and roofing contractors. We hope the information it contains will make you a more knowledgeable consumer and, when the time comes, a smart roof buyer. A new roof is a big investment. We want to help you get a good roof at a fair price from a professional roofing contractor. William A. Good, CAE
 There are a number of things to consider when selecting a new roof for your home. Of course, cost and durability head the list, but aesthetics and architectural style are important too. The right roof for your home is the one that balances those four considerations. ASPHALT SHINGLES--which possess an overwhelming share of the U.S. residential roofing market--can be reinforced with either organic or fiber glass materials. Although shingles reinforced with organic felts have been around much longer, fiber glass-reinforced products have come to dominate the market. Organic shingles consist of a wood-fiber base that is saturated with asphalt and coated with colored mineral granules. To fight fungus growth in warm, wet climates, they are available with special algicide granules. Fiberglass shingles consist of a fiberglass mat and top-and-bottom layers of asphalt and mineral granules. Typically, fiberglass offers greater durability, but their manufacture is important. The fire resistance of asphalt shingles, like most other roofing materials, is categorized by UL Class A, B, or C. Class A is the most fire resistant, while Classes B and C have less fire resistance. Generally, most fiberglass shingles have a Class A fire rating, while most organic shingles have a Class C rating. A shingle's reinforcement will have little effect on its appearance. Both organic and fiberglass products are available in laminated (architectural) grades that offer a textured appearance. Zinc granules also can be applied to either organic or fiberglass products to protect against algae (fungus) attack, a common problem in hot and humid parts of the country. Both types of shingles are also available in a variety of colors. WOOD SHINGLES AND SHAKES are made from cedar, redwood, southern pine, and other woods. Shingles are machine-sawn; shakes are hand-hewn and rougher looking. Their natural look is popular in California, the Northwest, and parts of the Midwest. Things to consider: some local codes limit their use, they have a UL fire rating of Class B or C (or none at all), and they should be treated with a preservative every three to five years to prevent decay. TILE--clay or concrete--is a durable but fairly expensive roofing material. "Mission-style" and "Spanish" round-topped tiles are widely used in the Southwest and Florida, and flat styles also are available to create French and English looks. Tile is available in a variety of colors and finishes. Note: Tile is heavy. If you are replacing another type of roof with tile, you will need to verify that the structure will support the load. SLATE is quarried in Vermont, New York, Pennsylvania, and Virginia, and in Canada. It comes in different colors and grades, depending on its origin. Considered virtually indestructible, it is, however, more expensive than other roofing materials. And, its application requires skill and experience. Many old homes in the Northeast still are protected by this long-lasting roofing material. METAL, primarily thought of as a commercial roofing material, has been found to be an attractive roofing alternative for homeowners. There are a variety of metal shingles intended to simulate traditional roof coverings, such as wood shakes, shingles and tile. Apart from metal roofing's longevity, metal shingles are relatively lightweight, typically have a Class A fire rating, have a greater resistance to adverse weather and can be quite aesthetically pleasing. SYNTHETIC ROOFING COVERINGS simulate various types of traditional roof coverings, such as slate and wood shingles and shakes. We recommend that you look at full-size samples of the proposed product, along with manufacturers' brochures, or visit a building that is roofed with that product, before making a buying decision.  All roofs have four basic components: Rafters (or trusses) are the "bones," sheathing is the first layer of protective "skin," the underlayment is the second layer, and the shingles (or other roof covering) the third layer.  Buying a new roof is an important investment. Before you spend your money, spend some time learning how to evaluate the roofing contractor who may be doing the work. You should insist on working with a professional roofing contractor. The National Roofing Contractors Association (NRCA) wants to assist you in getting the kind of results you expect--a quality roof at a fair price. All roofing contractors are not alike, and NRCA recommends that you prequalify your roofing contractor to get the job done right the first time. The following guidelines will help in your decision:
 All roofs have five basic components:
 One of the most critical factors in roof durability is proper ventilation. Without it, heat and moisture build-up in the attic area combine to cause rafters and sheathing to rot, roof shingles to buckle, and insulation to lose its effectiveness. It is therefore important never to block off sources of roof ventilation, such as louvers, ridge vents or soffit vents, even in winter. Proper attic ventilation will help prevent structural damage caused by moisture, increase the life of the roofing material, reduce energy consumption, and enhance the comfort level of the rooms below the attic. In addition to the free flow of air, insulation plays a key role in proper attic ventilation. According to the American Society of Home Inspectors, the ideal attic has:
The requirements for proper attic ventilation may vary greatly, depending upon the part of the country in which the home is located as well as the conditions at the home site, such as exposure to the sun, shade, and atmospheric humidity. Nevertheless, the general formula is based on the length and width of the attic itself. The minimum recommendation, set by the Federal Housing Authority is one square foot of free vent area for each 150 square feet of attic floor--if there is no vapor retarder under your insulation. With a vapor retarder you need half that amount. For more specific ventilation information, request a copy of The American Society of Home Inspectors' brochure, "Give Your Attic a Breath of Fresh Air."  SUN: Heat and ultraviolet rays cause roofing materials to deteriorate over time. The deterioration can occur faster on the sides facing west or south. RAIN: When water gets underneath the shingles, shakes or other roofing materials, it can work its way to the deck and cause the roof structure to rot. And, the extra moisture encourages mildew and rot elsewhere in the house, including damage walls, ceilings, insulation and even the electrical system. WIND: High winds can lift the edges of shingles (or other roofing materials) and force water--and debris--underneath them. Very high winds can do extensive damage. SNOW AND ICE: Melting snow often refreezes at the roof's overhang (where the surface is cooler), forming an ice dam and blocking proper drainage into the gutter. Instead, the water backs up under the shingles and seeps into the interior. In the early melt stages, gutters and downspouts can be the first to fill with ice and be damaged beyond repair or torn off the house. CONDENSATION: Condensation can result from the build-up of relatively warm moisture-laden air. Moisture in a poorly ventilated attic promotes decay of the wood sheathing and rafters, possibly destroying the roof structure. The solution may be to increase attic ventilation through the use of larger or additional vents, so that the attic air temperature will be closer to the outside air temperature. MOSS AND ALGAE: Moss can grow on wood shingles and shakes if they are kept moist by poor sunlight conditions or bad drainage. Once it grows, moss holds even more moisture to the roof surface, causing rot, and its roots actually work their way into the wood. Algae also grows in damp, shaded areas on wood or asphalt shingle roofs. Besides creating an ugly black-green stain, it can retain moisture, causing rot and deterioration. Trees and bushes should be trimmed away from the house to eliminate damp, shaded areas, and gutters should be kept clean to ensure good drainage. TREES AND LEAVES: Tree branches touching the roof will scratch and gouge the roof material as they are blown back and forth by the wind. Falling branches from overhanging trees can damage--or even puncture--shingles and other roof materials. Leaves on the roof surface retain moisture and cause rot, and leaves in the gutters block drainage. MISSING OR TORN SHINGLES: The key to a roof's effectiveness is complete protection. When shingles are missing or torn off, the roof structure and the interior of the home are vulnerable to water damage and rot. And the problem is likely to spread--nearby shingles are easily ripped or blow away. Missing or torn shingles should be replaced as soon as possible. SHINGLE DETERIORATION: When shingles get old and worn out, they curl, split, and lose their waterproofing effectiveness. And weakened shingles are easily blown off, torn or lifted by wind gusts. The end result is structural rot and interior damage. A deteriorated roof only gets worse with time and it should be replaced as soon as possible. FLASHING DETERIORATION: Many apparent roof leaks are really flashing leaks. Without good, tight flashings around chimneys, vents, skylights and wall/roof junctions, water can sneak into the house and cause damage to walls, ceilings, insulation and even the electrical system. Flashings should be checked as part of a twice-yearly roof inspection and gutter-cleaning.  Q. How can a homeowner recognize when a roof has problems? A. All too often, roof problems are discovered after leaking or other serious damage occurs. Periodic (twice-a-year) inspections can often uncover cracked, warped, or missing shingles, loose seams and deteriorated flashings, excessive surface granules accumulating in the gutters or downspouts, and other visible signs of roof problems. Indoors, look for cracked paint, discolored plasterboard, and peeling wallpaper as signs of damaged roof areas. Q. What are my options if I decide to reroof? A. You have two basic options. You can choose a complete replacement of the roof system, involving a tear-off of the old roof, or a re-cover over the existing roof, involving only the installation of a new membrane and surfacing. If you've already had one recover over your original roof, check with a professional roofing contractor to see if your deck can support a second recover. Q. My roof leaks. Do I need to have it totally replaced? A. Not necessarily. Leaking can result because some flashings have come loose or because a section of the roof has been damaged. A roof failure, however, is generally irreversible and results from improper installation or choice of materials, or from the installation of a roof system inappropriate to the building. Q. Can't I just do the work myself? A. Most work should not be do-it-yourself. Professional roofing contractors are trained to safely and efficiently repair or replace a roof. Novices can harm a roof with improper roofing techniques and severely injure themselves by falling off or even through a roof in need of repair or replacement. Homeowner maintenance should be confined to roof inspections in both the fall and spring to check for cracked or curling shingles, and to cleaning rain gutters filled with dead leaves and other debris. If you must see the roof for yourself, use a firmly braced or tied-off ladder equipped with rubber safety feet. Wear rubber-soled shoes and stay on the ladder (and off the roof) if possible. Q. How long can I expect my roof to last? A. The condition and lifespan of your roof will depend on the type of roof you have, the effects of your local environment and the maintenance which the roof has received. According the American Society of Home Inspectors, asphalt shingles generally last 15-20 years; wood shingle/shakes, 10-40 years; clay/concrete tiles, 20+ years; slate, 30-100 years; metal roofing, 15-40+ years. Roofing product manufacturers offer a variety of warranties on their products. Take a close look at those warranties to see what responsibilities and financial obligations they will assume if their products fail to reach their expected lifetimes. Q. What will a new roof cost? A. The price of a new roof varies widely, depending on the material selected, the contractor doing the work, the home itself, area of the country, local labor rates, time of year, and more. To get a good idea of the cost for your roof, get three or four estimates from reputable contractors in your area. Keep in mind that cost is only one factor, and it must be balanced against the quality of the materials and workmanship. For each roofing material there are different grades - and corresponding prices. Plus, there are a variety of styles and shapes. You need to look at the full product range and make a choice based on your budget and needs. Within the roofing profession there are different levels of expertise and craftsmanship. Pick a contractor who is committed to quality work. Q. How can I determine my annual cost? A. When mulling over your roofing options, the following formula may help:  DECK/SHEATHING: The surface--usually plywood or oriented-strand board (OSB)--to which roofing materials are applied.
DRIP EDGE: An L-shaped strip (usually metal) installed along the edges of the roof to allow water run-off to drip clear of the deck, eaves and siding.
FASCIA: A flat board, band, or face located at the outer edge of the cornice. FELT/UNDERLAYMENT: A sheet of asphalt-saturated material (often called "tar paper") used as a secondary layer of protection for the roof deck. FIRE RATING: The Underwriters Laboratories (UL) system for classifying the fire-resistance of various materials. Roofing materials are rated Class A, B, or C, with Class A materials having the highest resistance to fire originating outside the structure.
ORIENTED-STRAND BOARD/OSB: Roof deck panels (4ft. x 8 ft.) made of narrow bits of wood, laid down lengthwise and crosswise in layers, held together with a resin "glue." Often used as a substitute for plywood sheets. PENETRATIONS: Vents, pipes, stacks, chimneys - anything that sticks up through the roof deck.
RIDGE: The top edge of two intersecting sloping roof surfaces. SHEATHING: The boards or sheet materials which are fastened to the roof rafters to cover the house.
SQUARE: The common measurement for roofs: 100 square feet (10' x 10'). TRUSS: The engineered components which have supplemented rafters in many newer houses. They are designed for specific applications and cannot be cut or altered in any way.
VAPOR RETARDER: A material designed to restrict the passage of water vapor through a roof or wall. 
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